This invention relates to a vehicle dynamic control system which carries out warning and decelerating control in order to assist a vehicle in safely passing through a curve on a road in front of the vehicle.
Recently developed are several kinds of technology wherein road map data, provided from a navigator installed on a vehicle, are processed into road geometry data. Warning and decelerating controls are carried out after a judgement is made on the possibility of a vehicle passing through an approaching curve based on road data including the curvature of the curve and vehicle speed.
For example, Japanese Patent Laid-open No. 194886/1996 disclosed warning and vehicle speed control technology. Road data of a curve on a road are calculated based on road map data provided from a navigator. A permissible lateral acceleration allowable limit to enter into the curve and a foreseeable lateral acceleration at the entrance of the curve if the vehicle goes on at the present speed are calculated and compared. When the foreseeable lateral acceleration is larger than the permissible lateral acceleration, the present speed is judged as too high to enter into the curve, namely an over speed condition, and a warning and vehicle speed control are carried out.
When judging the possibility of passing through a curve, the approaching road to the curve is deemed to be a straight line and certain deceleration is applied to reduce an initial speed to a speed which is slow enough to allow the vehicle to safely pass through the curve.
Thinking about a case where the road to the objective curve is not a straight line, the judgement may not be made accurately by the calculation. In the case where the road is not a straight line, lateral acceleration occurs on the vehicle, resulting in forced reduction of deceleration based on a relation between longitudinal acceleration and lateral acceleration. Thus, an over speed judgement may be allowed by the system.
In order to eliminate the influence of the error, it may be a countermeasure to calculate permissible decelerations for all bends and then carry out the control. But as enormous calculations then would be required, processing speed becomes too slow for practical use.